Process and apparatus for the combustion of fuels

ABSTRACT

A combustion process and combustion chamber design for the improved combustion of liquid fuels is shown. By means of this process very high specific combustion chamber loads are attainable providing an economically optimal and silent combustion. The chamber is annular wherein the fuel-air mixture is injected in the form of at least one jet in a secantal direction into the combustion chamber thus producing a rotating stream, and discharges the gases from the combustion chamber at right angles thereto. Thus by means of injecting the fuel-air mixture in a secantal direction and the annular combustion chamber designs there is a complete mixing of the fuel-air mixture resulting in complete combustion of the fuel particles.

United States Patent Inventor Lothar P. Brenner Luzern, Switzerland Appl. No. 862,862

Filed Oct. 1, 1969 Patented Oct. 5, 1971 Assignee Anmelderin Ygnis S. A.

Fribourg, Switzerland Priority Oct. 1, 1968, Sept. 5, 1969 Switzerland 14741/68 and 13457/69 PROCESS AND APPARATUS FOR THE [5 6} References Cited UNITED STATES PATENTS 2,539,165 1/1951 Saha 431/173 X 3,185,202 5/1965 Mitchell et a1. 431/ 173 X FOREIGN PATENTS 1,079,260 4/1960 Germany 110/28 Primary ExaminerEdward G. Favors Attorney-Browdy and Neimark ABSTRACT: A combustion process and combustion chamber design for the improved combustion of liquid fuels is shown. By means of this process very high specific combustion chamber loads are attainable providing an economically optimal and silent combustion. The chamber is annular wherein the fuel-air mixture is injected in the form of at least one jet in a secantal direction into the combustion chamber thus producing a rotating stream, and discharges the gases from the combustion chamber at right angles thereto. Thus by means of injecting the fuel-air mixture in a secantal direction and the annular combustion chamber designs there is a complete mixing of the fuel-air mixture resulting in complete combustion of the fuel particles.

COMBUSTION OF FUELS 23 Claims, 15 Drawing Figs.

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PROCESS AND APPARATUS FOR THE COMBUSTION F FUELS The present invention concerns a process for the combustion of liquid fuels, and further concerns a combustion chamber, particularly in boilers, for the performance thereof.

The object of the present invention is to provide a process which, being for the combustion of liquid fuels in a combustion chamber, covers a wide capacity range and which, when employed in a combustion chamber, particularly in that of a highload boiler, ensures an economically optimal and silent combustion. A further object is to attain very high specific combustion chamber loads and ensure a high, yet uniform heat distribution of the combustion chamber wall.

The said process essentially consists in introducing the fuelair mixture in the form of at least one jet in a secantal direction into a combustion chamber which has at least approximately the shape of an annular body and is devoid of refractory material and is cooled, and producing a rotating stream and discharging the combustion gases in the zone of the rotating stream axis, the whole arrangement being such that any contact of liquid particles with the wall is prevented and, owing to the rotary motion, no unbumt fuel particles can leave the combustion chamber, and that an optimal forced recirculation of the hot combustion gases into the ignition zone is ensured.

The combustion chamber for the performance of the said process is characterized in that it has a mainly annular symmetrical shape and is provided with at least one burner arranged secantally with respect to it for developing a rotary stream, and that it is further provided with at least one flue outlet in the zone of the rotary stream axis.

The said invention is now to be illustrated by way of example with reference of the following diagrammatic drawings, in whichFIG. 1 shows a vertical section through a boiler for liquid fuels, along line I--I in FIG. 2;

, FIG. 2 shows a section through the-boiler along line IIII in FIG. 1;

FIG. 3 shows a cross section through the boiler along line III-Ill in FIG. 1;

FIG. 4 shows a longitudinal section through a horizontal boiler along line lV-IV in FIG. 5;

FIG. 5 shows a cross section through the boiler along line IIIIII in FIG. 4;

FIGS. 6-11 show various modifications of combustion chambers in vertical section;

FIG. 12 shows a longitudinal section through a boiler for liquid fuels along line Il-Il in FIG. 13;

FIG. 13 shows a section through the boiler along line [-1 in FIG. 12;

FIG. 14 shows the startup vibrations in the combustion chamber of a known prior art boiler system; and

FIG. 15 shows the startup vibrations, recorded by the same method, of the boiler according to the invention.

The boiler represented in FIGS. l-3 has a combustion chamber 1 which is completely immersed in water and which, in the embodiment shown, has a practically hollow-spherical shape, but which may also be cylindrical or double-conical. The said combustion chamber 1 presents a burner tube orifice 5 with a burner axis 3. A burner tube stub 7 is provided at its free end with a flange 9 for attaching a blower 11. In FIG. 2, the end of a mixing device 13 of the burner is visible. Leading from the combustion chamber 1 are two outlets 15 and 17, which are arranged symmetrically with respect to each other and which practically have a common horizontal axis 19 which is also a main axis of the combustion chamber 1.

The combustion chamber outlets 15 and 17 lead into a convection heating space 21 which extends in semicircular fashion around a boiler water jacket 31 of the boiler. The said convection heating space ends at a common flue stub 23. Two cleaning stubs 25 and 27 give access to the convection heating space 21. The combustion chamber wall 29 separates the combustion space from the boiler water 33. The convection heating space 21 is provided with water tubes 35. The boiler has a main vertical axis 37 which is perpendicular to the burner axis 3, which itself is parallel to the combustion chamber outlet axis 19. The dome above the boiler water carries a steam extraction stub 39. A feed water stub 41 conducts the feed water through the side of the boiler water jacket 31. The said boiler with the combustion chamber 1 and the jacket 31 is provided with a shell 43 for insulation and protection.

The burner axis 3 is offset with respect to the combustion chamber axis 19, so that the flame with the combustion air enters the combustion chamber 1 in a secantal direction and is deflected by the combustion chamber wall 29 and thus forced into a circular path. The flue gases pass through the two outlets l5 and 17 on opposite sides of the combustion chamber, 1 into the convection heating space 21, where, having transferred a substantial part of their heat to the water tubes 35, they meet in the flue stub 23, which conducts them to the chimney (not shown). I

In this manner, there arise in the combustion chamber 1 two rotary streams which have symmetrical paths with respect to the plane through the axis 37 and the axis 3. In addition to the radiation, high tangential velocities result in a considerable amount of convective heat transfer. The rotary motion (increased turbulence) results in a very good heat transfer in the immediately following flue gas zone.

The boiler shown in FIGS. 4 and 5 is also provided with a spherical combustion chamber 1, into which the burner tube stub 7 (with burner axis 3) leads in secantal direction. The blower 11 is attached to the burner tube stub 7 by the flange 9. The combustion chamber wall 29 is spherical. The longitudinal section through the boiler in FIG. 4 further shows the boiler shell 46 and, surrounded by the latter, a jacket 48 for the outer delimitation of a water chamber 49. Communicating with the water chamber 49 are an outlet line stub 50 and a retum-line stub 52. In this embodiment again, the combustion chamber 1 has two opposite outlets 54 and 55 with a common axis 19. These two outlets 54 and 55 lead into a lower flue gas chamber 57, from which the flue gas tubes 58 lead into an upper flue gas chamber 59. The two flue gas chambers 57 and 59 are separated from each other by a partition 61. Located in the rear portion of the water chamber 49 are, as shown in FIG. 4, the flue gas tubes 58, arranged in two mutually parallel vertical nests, between which (FIG. 5) a hot service water unit 63 with cells 64 is arranged. Having passed through the flue gas tubes 58, the flue gases collect in the flue gas chamber 59 and leave it through a flue 66.

FIGS. 6 and 7 show two combustion chambers 70 with walls 71, each wall comprising a curved portion 73, 74 and an intermediate cylindrical central portion 75. Coaxial outlet stubs 77 and 78 arranged opposite each other permit the divided masses to pass out in opposite directions. The two outlet stubs 77 and 78 protrude into the combustion 70 and have ring jackets 80 carrying cooling water. FIGS. 6 and 7 further show the burner tube stub 82, which is so arranged with respect to the particular combustion chamber that a rotary motion is imparted to the media entering the combustion chamber, and the said rotary motion, acting in conjunction with the two mutually opposite outlet stubs 77 and 78, results in opening up the flame and mixing it with combustion air, fuel and combustion gases.

The version shown in FIG. 6 is provided with a baffle 84 which serves to guide the flow.

The purpose of the rings 86 and 87 arranged in the combustion chamber 70 according to FIG. 7 is to limit or dampen cross-streams, such as are known as secondary streams in connection with rotary streams.

In FIG. 8, the combustion chamber 90 is spherical. There again, the two outlet stubs 92 and 93 are coaxial and arranged opposite each other, and both protrude somewhat into the combustion chamber 90. They are screened by baffles 95 and 96 in order to prevent short-circuit streams and ensure that the flue gases follow the path indicated by the arrows. This version is advantageous in the case of extremely high combustion chamber loads.

The combustion chamber 98 shown in FIG. 9 is cylindrical. Again, it has two outlet stubs 100 and 101, provided with water-carrying ring jackets 103 and 104.

The version shown in FIG. 10 is a combination of the version according to FIG. 8 with outlet stubs according to FIG. 9,

while the version in FIG. 11 has a spherical combustion chamber 107 whose middle portion, into which the burner leads, is provided with a depression 108 intended to give the combustion chamber and, accordingly, the flame pattern, a more advantageous division.

In some versions, the outlet stubs extend into thecombustion chamber in order to ensure that gases streaming along in the fringe zone of the combustion chamber are returned to the proximity of the hot ignition zone 6, FIG. 1, of the rotating flame.

The boiler shown in FIGS. 12 and 13 again has a spherical combustion chamber 110, into which a burner tube stub l 12 is secantally introduced. The oil burner (not shown) is secured to the burner tube stub 112 by means of the flange 9. The combustion chamber wall 111 is spherical. The longitudinal section through the boiler shown in FIG. 12 further shows a combustion chamber outlet 116 leading into a flue gas deflection chamber 118, and water-cooled flue gas tubes 120 communicating with a flue gas collecting chamber 122. A flue stub 124 serves to discharge the flue gases into the chimney (not shown). As may be seen from the section along line II-II (FIG. 13),each flue gas tube 120 is jacketed along part of its length by a water-carrying tube 126. The water circulation through this combination of flue gas tubes 120 and water tubes 126 is effected through connecting stubs 128. Cleaning the boiler on the flue-gas side is effected through cleaning apertures 130 and through a cleaning aperture 134 giving access to the flue gas deflection chamber 118 protected by firebrick 132. It is known that the startup pattern of oil burners and also the silencing of boilers can be greatly influenced by the acoustic capacity of the combustion chamber and the acoustic inductivity of the convection heating surface. The

new insight here is that it is possible to greatly reduce the startup vibrations by devising an appropriate circulation such as is produced according to the present invention in a rotatingsymmetrical combustion chamber, particularly one that is similar to a hollow sphere.

Extensive experiments have confirmed that the inherent attenuation in such a combustion chamber can be up to 40 percent better than that in known combustion chambers. FIG. 14 shows a startup vibration such as arises in a modern highcapacity boiler, while FIG. 15 shows the startupvibration of the new combustion chamber with direct-following convection heating surface. As the design of the blower depends mainly on the magnitude of the startup vibrations, and not on the static positive pressure in the combustion chamber, it is possible to use cheaper oil burners in conjunction with such a combustion chamber.

In the known oil burner mixing systems, the oil flame lacks air in its core, while there is an air surplus in its fringe zone, and so it is desirable and expedient to devise a combustion chamber which improves the mixing of combustion air and oil particles, which is not naturally uniform because of the fuel distribution in the form of jets. This is achieved by an arrangement wherein the fuel particles introduced in secantal direction into a rotation-symmetrical, preferably hollowspherical combustion chamber are almost ideally mixed with the combustion air with the aid of the combination of circumferential, radial and wall-near cross-streams prevailing in the chamber. This good mixing, combined with a forced and optimal recirculation of combustion gases into the ignition zone (shown in FIG. 1), intensifies the combustion process. This effect can be further improved by dividing the flame in the manner described by arranging combustion chamber outlets opposite each other, as shown in FIGS. 1 and 3. This improves the mixing effect and, accordingly, the combustion process.

In known systems, refractory material is used in combustion chambers with a view to ensuring the ignition and reducing the reaction time of the fuel-air mixture.

Under the present invention, however, the high mixing effect and the return of hot combustion gases into the ignition zone eliminates the need for refractory material in the combustion chamber. Another special advantage of this system is that the burning rate in such a combustion chamber is so great that no flames escape from the chamber, despite the high specific chamber load. And so it is also possible to arrange the contact heating surfaces directly after the outlet for the gases from the combustion chamber.

Another feature of this system is that the axis of the rotary stream produced coincides at least approximately with the axis of the combustion chamber outlet.

The foregoing description shows that the combustion chamber need'not have any refractory material or fittings or guide plates, which means that heat buildups as well as imnecessary pressure losses can be avoided.

There are known cyclone firing systems for solid fuels whose main process feature is the near-complete separation of the ash particles liquified by the high combustion chamber temperature in the combustion chamber or on the hot combustion chamber wall, for the purpose of reducing contamination of the direct-following heating surface. 1

However, the combustion chamber under the present invention differs from the known firing systems in that the liquid fuel particles introduced in secantal direction into the chamber cannot touch the cooled chamber wall, so that coke deposition is with certainty prevented.

The properties of the combustion chamber described are achieved mainly by observing the following geometrical rela tions:

Distance of burner axis 3 from rotation axis 19 of combustion chamber: 0.] to 0.4 D;

Distance of burner noule from vertical plane to burner axis 3 and through rotation axis 19: 0.25 to 0.5 D;

Maximum combustion chamber extent in direction of rota- .tion axis 19: L5 D;

in a direction perpendicular to the rotation axis 19 of the chamber.

I claim:

1. A process for the combustion of fuels, said process comprising the steps of introducing at least one jet of a fuel-air mixture in a secantal direction into a hollow substantially annular combustion chamber and thereby producing a rotary stream of the mixture for combustion, and dividing the rotary stream and discharging the thus divided combustion gases'in different direction substantially along the rotary stream axis to exits provided at each end zone of the rotary stream axis.

2. A process as defined in claim I, wherein the fuel-air mixture is introduced into a hollow substantially spherical combustion chamber.

3. A process as defined in claim 1, wherein the fuel-air mixture is introduced into a hollow substantially cylindrical combustion chamber.

4. A process as defined in claim 1, wherein the fuel-air mixture is introduced into a hollow substantially double frustoconical combustion chamber.

5. A process as defined in claim 1, wherein the combustion gases are divided in a plane which is at least approximately perpendicular to the rotary stream axis.

6. A combustion chamber particularly for boilers comprising a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the distance of the burner nozzle from the perpendicular to the burner axis through the rotational axis of the chamber is 0.25 to 0.5 of the maximum chamber inside diameter (D), with D meaning the maximum chamber inside diameter in a direction perpendicular to the rotational axis.

7. A combustion chamber particularly for boilers comprising a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the distance of the burner axis from the rotational axis of the chamber is 0.1 to 0.4 D, with D meaning the maximum chamber inside diameter in a direction perpendicular to the rotational axis.

8. A combustion chamber particularly for boilers compriss ing a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the maximum inside measurement of said chamber in the direction of the rotational axis does not exceed 1.5 times the maximum chamber inside diameter (D).

9. A combustion chamber particularly for boilers comprising a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the total flue gas outlet cross section does not exceed 50 percent of the maximum cross section pi 0 /4 of the chamber interior.

it). A combustion chamber particularly for boilers comprising a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the distance of the burner axis from the nearest flue gas outlet does not exceed 0.75 D.

11. A combustion chamber comprising a hollow substantially annular combustion chamber, at least one burner for introducing at least one jet of a fuel-air mixture in a secantal direction into said hollow substantially annular combustion chamber, a rotary stream of the mixture for combustion thereby being produced, exit means provided to either side of said burner at each end zone of the rotary stream axis, the combustion gases being divided and discharged in different directions substantially along the rotary stream axis to said exits.

12. A combustion chamber as defined in claim 11 wherein said exits define flue gas outlets and wherein the axes of said flue gas outlets are parallel to the axis of said rotary stream and substantially coincide therewith.

13. A combustion chamber as defined in claim 11 wherein said exits define flue gas outlets and wherein each flue gas outlet is provided with stubs protruding into the interior of said combustion chamber.

14. A combustion chamber as defined in claim 11, said combustion chamber having a hollow spherical interior.

15. A combustion as defined in claim 11, wherein said combustion chamber defines a cylindrical interior.

16. A combustion chamber as defined in claim 11 wherein said combustion chamber defines a double frustoconical interior.

17. A combustion chamber as defined in claim 11 wherein said exits define flue gas outlets, said flue gas outlets leading into a common annular flue stream.

18. A combustion chamber as defined in claim 17, wherein said common flue stream is traversed by fluid-containing tubes.

19. A combustion chamber as defined in claim 11, wherein the walls of said combustion chamber comprise a single layer of bare metal.

20. A combustion chamber as defined in claim 13, wherein said flue gas outlet stubs are cooled.

21. A combustion chamber as defined in claim It further including cross-stream dampening means in the interior of said combustion chamber.

22. A combustion chamber as defined in claim 11, wherein deflecting means are arranged before said discharge exits in the interior thereof.

23. A combustion chamber as defined in claim 11, wherein said discharge exits define outlet stubs and wherein each outlet stub coaxially leads into a flue gas deflection chamber. 

2. A process as defined in claim 1, wherein the fuel-air mixture is introduced into a hollow substantially spherical combustion chamber.
 3. A process as defined in claim 1, wherein the fuel-air mixture is introduced into a hollow substantially cylindrical combustion chamber.
 4. A process as defined in claim 1, wherein the fuel-air mixture is introduced into a hollow substantially double frustoconical combustion chamber.
 5. A process as defined in claim 1, wherein the combustion gases are divided in a plane which is at least approximately perpendicular to the rotary stream axis.
 6. A combustion chamber particularly for boilers comprising a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the distance of the burner nozzle from the perpendicular to the burner axis through the rotational axis of the chamber is 0.25 to 0.5 of the maximum chamber inside diameter (D), with D meaning the maximum chamber inside diameter in a direction perpendicular to the rotational axis.
 7. A combustion chamber particularly for boilers comprising a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the distance of the burner axis from the rotational axis of the chamber is 0.1 to 0.4 D, with D meaning the maximum chamber inside diameter in a direction perpendicular to the rotational axis.
 8. A combustion chamber particularly for boilers comprising a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the maximum inside measurement of said chamber in the direction of the rotational axis does not exceed 1.5 times the maximum chamber inside diameter (D).
 9. A combustion chamber particularly for boilers comprising a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the total flue gas outlet cross section does not exceed 50 percent of the maximum cross section pi D2/4 of the chamber interior.
 10. A combustion chamber particularly for boilers comprising a substantially annular symmetrical shape, said combustion chamber being provided with at least one burner disposed secantally with respect to said chamber for developing a rotary stream, said combustion chamber having at least one flue gas outlet in the zone of the rotary stream axis, and wherein the distance of the burner axis from the nearest flue gas outlet does not exceed 0.75 D.
 11. A combustion chamber comprising a hollow substantially annular combustion chamber, at least one burner for introducing at least one jet of a fuel-air mixture in a secantal direction into said hollow substantially annular combustIon chamber, a rotary stream of the mixture for combustion thereby being produced, exit means provided to either side of said burner at each end zone of the rotary stream axis, the combustion gases being divided and discharged in different directions substantially along the rotary stream axis to said exits.
 12. A combustion chamber as defined in claim 11 wherein said exits define flue gas outlets and wherein the axes of said flue gas outlets are parallel to the axis of said rotary stream and substantially coincide therewith.
 13. A combustion chamber as defined in claim 11 wherein said exits define flue gas outlets and wherein each flue gas outlet is provided with stubs protruding into the interior of said combustion chamber.
 14. A combustion chamber as defined in claim 11, said combustion chamber having a hollow spherical interior.
 15. A combustion as defined in claim 11, wherein said combustion chamber defines a cylindrical interior.
 16. A combustion chamber as defined in claim 11 wherein said combustion chamber defines a double frustoconical interior.
 17. A combustion chamber as defined in claim 11 wherein said exits define flue gas outlets, said flue gas outlets leading into a common annular flue stream.
 18. A combustion chamber as defined in claim 17, wherein said common flue stream is traversed by fluid-containing tubes.
 19. A combustion chamber as defined in claim 11, wherein the walls of said combustion chamber comprise a single layer of bare metal.
 20. A combustion chamber as defined in claim 13, wherein said flue gas outlet stubs are cooled.
 21. A combustion chamber as defined in claim 11 further including cross-stream dampening means in the interior of said combustion chamber.
 22. A combustion chamber as defined in claim 11, wherein deflecting means are arranged before said discharge exits in the interior thereof.
 23. A combustion chamber as defined in claim 11, wherein said discharge exits define outlet stubs and wherein each outlet stub coaxially leads into a flue gas deflection chamber. 